PROJECT SUMMARY The purpose of this project is to better understand the mechanisms contributing to HIV-1 persistence, and therefore to identify novel therapeutic targets that could lead to an ultimate HIV-1 cure. The hypothesis being tested is that HIV-1 persistence is largely due to resistance of HIV-1 infected cells to apoptosis, or programmed cell death, due to expression of anti-apoptotic BCL2 proteins. This concept is highly innovative, as other investigators trying to determine why the ?kick and kill? strategy for HIV-1 cure has not worked to date have focused on optimizing the effectiveness of latency reversal agents or immune effector cell (CD8 T cell or NK cell) function to reduce the persistent HIV-1 reservoir. However, these strategies are unlikely to work even if optimized due to resistance of the infected cells to apoptosis. Innovation in this concept is extended by exploring the roles of multiple anti-apoptotic BCL2 proteins, including BCLXL and MCL1 which have not been previously studied in depth and the effect of latency reversal agents themselves on apoptosis sensitivity in reactivated cells. In addition, we investigate the mechanisms underlying individual variations in expression of these anti-apoptotic proteins, which before were assumed to be uniform across cells and persons. Three specific aims are proposed: 1) Anti-apoptotic BCL2 proteins contribute to HIV-1 persistence by preventing apoptosis in infected cells and promoting viral production; 2) HIV-1 latency reversal decreases apoptosis susceptibility in infected cells; 3) Determine host and cellular factors regulating anti-apoptotic BCL2 protein expression. The long term objective of the proposed studies is to identify one or more translatable strategies to reduce the HIV-1 reservoir size through improved understanding of the role and mechanisms of anti-apoptotic BCL2 proteins contributing to HIV-1 persistence. The results of these studies will significantly advance current and future investigational efforts to specifically kill latently HIV-1 infected cells, and therefore have an immediate and lasting impact on the search for an HIV-1 cure.